Hematology and Hemostasis: Blood Components and Testing

1. 1 Introduction

2. Learning Objectives At the end of this unit of study, the student should be able to: • Compare the reference intervals for hemoglobin, hematocrit, erythrocytes, and leukocytes in infants, children, and adults. • Identify the function of erythrocytes, leukocytes, and platelets. • Describe the composition of blood. continued on next slide

3. Learning Objectives At the end of this unit of study, the student should be able to: • Explain the causes of change in the steady state of blood components. • Describe reflex testing, and identify the laboratory's role in designing reflex testing protocols. • Define hemostasis and describe the result of an upset in the hemostatic process. continued on next slide

4. Learning Objectives At the end of this unit of study, the student should be able to: • Identify hematology and hemostasis screening tests. • List the three components of laboratory testing and correlate errors with each component.

5. Hematology • Study of cellular components of blood • Includes: • Normal and abnormal development • Physiology • Function • Reaction to disease • Death or destruction of the formed elements of the blood

6. Composition of Blood • Plasma • Liquid component (55% of the blood volume) • Water, ions, proteins, carbohydrates, fats, hormones, vitamins, enzymes

7. Composition of Blood • Cellular elements (45% of the blood volume) • Erythrocytes, leukocytes, platelets • The normal adult has about 6L of blood • Approximately 7–8% of total body weight

8. Plasma • Contains ions necessary for cell function • Calcium, sodium, potassium, chloride, magnesium, hydrogen • Contains proteins • Albumin, immunoglobulins, complement, coagulation proteins • Acts as a transport medium for cell nutrients and metabolites

9. Cellular Components • Red blood cells (RBCs) • Erythrocytes • Contain hemoglobin which transports O2 and CO2

10. Cellular Components • White blood cells (WBCs) • Leukocytes • Defense against foreign antigens such as bacteria and viruses

11. Cellular Components • White blood cells (WBCs) • Five major types • Neutrophils • Lymphocytes • Monocytes • Eosinophils • Basophils

12. Cellular Components • Platelets • Thrombocytes • Necessary for hemostasis

13. Reference Ranges • Physiologic differences in "normal values" may occur due to: • Race, age, gender, and geographic location • Example: Newborns when compared to adults have a: • Higher RBC concentration • Higher hemoglobin • Higher WBC count

14. Reference Ranges • Pathologic changes may occur as the result of disease or injury.

15. Reference Ranges • Each laboratory must establish their own reference ranges. • Determined by: • Calculating the mean value from a group of healthy individuals • Reference range will be the mean +/- 2 standard deviations • 95% of normal individuals test values will fall within this range

16. Hemostasis • Process of forming a blood clot to stop blood loss • Stages of hemostasis • Primary hemostasis, secondary hemostasis, fibrinolysis • Requires interactions by: • Platelets, blood vessels, proteins

17. Hemostasis • An upset in any stage can cause: • Bleeding or abnormal clotting (thrombosis)

18. Blood Component Therapy • Therapy for hematologic and nonhematologic disorders • Whole blood collected from donors can be separated into: • Packed RBCs • Platelets • Fresh frozen plasma (FFP) • Cryoprecipitate • Granulocytes

19. Table 1-1 Blood Components and Their Uses

20. Components of Laboratory Testing • Pre-examination (pre-analytical) • All aspects of testing that occur prior to testing that affect outcomes. • Examination (analytical) • All factors that affect test procedures. • Post-examination (post-analytical) • All factors that affect testing after completion of the test.

21. Investigation of a Problem • Physician will: • Take a medical history • Perform physical exam • Order laboratory tests as indicated above

22. Investigation of a Problem • Laboratory tests can be: • Screening tests • Specific tests • Ordered based on results of screening tests • Repeat tests • Ordered to track disease progression, evaluate treatment, identify side effects and complications, or assist in prognosis

23. Hematology Screening Tests • Complete blood count (CBC) • Quantifies the: • WBCs, RBCs, Hemoglobin (Hgb), Hematocrit (HCT), Platelets • Calculates the RBC indices: • From the RBC count, Hgb, and HCT • Defines the size and hemoglobin content of the RBCs

24. Hematology Screening Tests • Complete Blood Count (CBC) • WBC differential • Enumerates the five types of WBCs • Morphology of RBCs and platelets

25. Hemostasis Screening Tests • Hemostasis • Tests that determine the time it takes to form a clot • Platelet count • Prothrombin time (PT) • Activated partial thromboplastin time (APTT)

26. Reflex Testing • Follow-up testing due to the results of screening tests • Laboratory must design reflex testing protocols for common diseases. • Called algorithms

27. Case Study—Chapter 1 • 2-year-old male • 102–104°F fever over the past 24 hours • Lethargic • Had been in good health except for two episodes of otitis continued on next slide

28. Case Study—Chapter 1 • Questions • Why might the pediatrician order lab tests? • How might the child's condition affect the composition of his blood?